Michael Edwards laughs along with the joke about the need for 10 tenors, as opposed to some lesser number.

But the idea might just touch a nerve. Edwards, it seems, once was the 11th tenor.

"I was actually brought on as an understudy," the affable Edwards said of his beginnings with the Australian vocal group the Ten Tenors, who perform March 23 at the Admiral Theatre. "I was kind of insurance in case somebody left."

That wasn't long Edwards found himself promoted into the Title Ten, and he's been touring with full portfolio (or in this case songbook) for three and a half years.

"Fortunately for me, there was an opening not long after I had become the understudy," Edwards said during a phone conversation from Scottsdale, Ariz., where the Ten Tenors were already a week into their current two-month bus tour. "My mum had a few of their albums, and it always had been kind of a dream of mine to join one day."

Turns out there's a perfectly good explanation why there are 10 tenors, and not nine, or any more, or any fewer.

Michael Edwards has been one of the Ten Tenors for 3 1/2 years, and is already on his fifth American tour.(Photo: Contributed photos)

"The group was first put together to perform for the 10th birthday of Channel 10 in Australia," an impressively well-versed Edwards explained. "They thought it would be a good joke to have 10. That's really all there is to it."

On the current American road swing, the Tenors will be concentrating on material from the CD "Wish You Were Here," released in the U.S. on March 2. Already having achieved No. 1 status in Australia, the album is a collection of songs made famous by artists who passed away before their time.

"The idea came about two years ago, when we were rehearsing the (David Bowie) song ‘Heroes,' which happened to be going into our show," Edwards said. "When we found out that Bowie had died, we started thinking about all these really significant artists who had been taken away, many of them too soon."

The album covers songs by or associated with Queen's Freddie Mercury, Prince, Michael Jackson, Whitney Houston, John Lennon, Michael Hutchence (of the Australian rock band INXS), Roy Orbison and others.

Edwards said the Freddie Mercury tribute, "We Are the Champions," is a particular favorite of his.

"It's a really interesting arrangement," said Edwards, who earned his bachelor's degree from the Melbourne Conservatory of Music not long before finding his way into the Ten Tenors lineup. "Stephen (Baker, the group's original pianist, now based in London) does all our arrangements. He's done a lot of film scoring, and he's really done an epic arrangement for this one."

Accompaniment comes from a combination of live musicians and pre-recorded backing tracks. The two longest-tenured tenors, Paul Gelsumini (joined in 2010) and Keane Fletcher (2011), serve as touring music director and director/choreographer, respectively.

But the show — who sings what, with who else — comes down to Baker.

"Rehearsals are very collaborative," Edwards said, "but it's Stephen who has the last word. He knows the voices, he knows what's going to work for each song."

Each of the tenors sings a solo spot, with the rest of the show a combination of duets and other combinations, including a bunch of segments with all 10 going at once.

"It's fun to be a part of," Edwards said, "especially when we get that full sound."

There might even be times when it sounds like there's 11 of them up there.